Chemical Change

What is the primary distinction between a chemical change and a physical change?

• A chemical change alters the state of matter, while a physical change creates a new substance.

• A chemical change results in a new substance with different properties, while a physical change alters only the form or appearance.

• Both chemical and physical changes involve the formation of new bonds.

• Physical changes are always reversible, whereas chemical changes are always irreversible.

Which of the following observations most strongly suggests that a chemical change has occurred?

• A substance changes from a liquid to a gas.

• A solid dissolves in a liquid.

• A new color appears when two clear liquids are mixed.

• A substance is crushed into smaller pieces.

When paper is burned, it transforms into ash and smoke. This process is best classified as what type of change?

• A physical change, because the paper's state of matter is altered.

• A chemical change, because new substances (ash and smoke) are formed.

• A physical change, because the original paper can be recovered.

• A chemical change, because the temperature increases.

Which of the following scenarios describes a physical change?

• A metal object develops rust after being exposed to moisture.

• A piece of fruit begins to rot and change color.

• Sugar crystals disappear when stirred into hot water.

• A candle wick burns, producing light and heat.